1. Field of the Invention
This invention relates to internal combustion engine crankcase structures, and particularly, to a structural oil pan having a provision for cross bolting to the main bearing caps.
2. Description of the Relevant Art
Internal combustion engines of the reciprocating piston type may have crankcase structures, or blocks, in which the side walls of the block extend to the center line of the crankshaft. In such an instance, the port ion of the engine extending below the center line of the crankshaft is housed in the space established by the engine oil pan. To stiffen and strengthen crankcase castings, as may be required by high performance applications, the side walls may be extended below the center line of the crankshaft. In a deep side wall crankcase, the main bearing caps typically are slidingly engaged along their side edges by ribbed portions of the extended side walls. Cross bolting of the bearing caps through the extended side walls reduces torsional distortion and vibration.
In the case of cast iron engine blocks, the extension of the side walls to increase strength and reduce vibration and noise requires a corresponding increase in engine weight. Weight increases in automotive applications are undesirable due to the effect on efficiency. In addition, existing engine crankcases having standard length side walls cannot easily be transformed to longer side walls without significant redesign and retooling expense.